Editing Orinoco (section)

== Geography ==

The course of the Orinoco forms a wide ellipsoidal arc, surrounding the [[Guiana Shield]]; it is divided in four stretches of unequal length that very roughly correspond to the longitudinal zonation of a typical large river: 
* '''Upper Orinoco''' – {{convert|286|km|mi}} long, from its headwaters to the Raudales de Guaharibos rapids, flows through mountainous landscape in a northwesterly direction
* '''Middle Orinoco''' – {{convert|805|km|mi}} long, divided into two sectors, the first of which ca. {{convert|515|km|mi}} long has a general westward direction down to the confluence with the [[Atabapo River|Atabapo]] and [[Guaviare River|Guaviare]] rivers at [[San Fernando de Atabapo]]; the second flows northward, for about {{convert|290|km|mi}}, along the Venezuelan–Colombian border, flanked on both sides by the westernmost granitic upwellings of the Guiana Shield which impede the development of a flood plain, to the [[Raudales de Atures|Atures rapids]] near the confluence with the [[Meta River]] at [[Puerto Carreño]]
*'''Lower Orinoco''' – {{convert|959|km|mi}} long with a well-developed alluvial plain, flows in a northeast direction, from Atures rapids down to Piacoa in front of [[Barrancas del Orinoco|Barrancas]]
* '''Delta Amacuro''' – {{convert|200|km|mi}} long that empties into the [[Gulf of Paría]] and the Atlantic Ocean, a very large [[river delta|delta]], some {{convert|22500|km2|mi2|-2|abbr=on}} and {{convert|370|km|mi|-1}} at its widest.

[[File:Deltaorinoco.jpg|thumb|right|Orinoco in Mariusa National Park (Delta Amacuro)]]
[[File:Ciudad guyana.jpg|thumb|right|Orinoco at its confluence with the [[Caroní River]] (lower left)<ref>{{cite web
  | url=http://earthobservatory.nasa.gov/IOTD/view.php?id=6215
  | title=Ciudad Guayana, Venezuela : Image of the Day
  | publisher=earthobservatory.nasa.gov | access-date=2009-10-31
| date=2006-01-23
  }}</ref>]]
[[File:Orinoco-Landschaft.JPG|right|thumb|Rapids of the Orinoco, near Puerto Ayacucho airport, Venezuela]]
[[File:Orinoco 33. 2005.jpg|right|thumb|Orinoco in [[Amazonas (Venezuelan state)|Amazonas State]], Venezuela]]
[[File:Orinoco4.jpg|right|thumb|Orinoco in Amazonas State, Venezuela]]

At its mouth, the Orinoco River forms a wide delta that branches off into hundreds of rivers and waterways that flow through {{convert|41,000|km2|-3|abbr=on}} of swampy forests. In the rainy season, the Orinoco River can swell to a breadth of {{convert|22|km|0}} and a depth of {{convert|100|m|-1}}.

Most of the important Venezuelan rivers are tributaries of the Orinoco River, the largest being the [[Caroni River (Venezuela)|Caroní]], which joins it at [[Puerto Ordaz]], close to the [[Llovizna]] Falls. A peculiarity of the Orinoco river system is the [[Casiquiare canal]], which starts as an arm of the Orinoco, and finds its way to the [[Rio Negro (Amazon)|Rio Negro]], a tributary of the [[Amazon River|Amazon]], thus forming a 'natural canal' between Orinoco and Amazon.

The [[stream gradient]] of the entire river is 0.05% (1,047 m over 2,250&nbsp;km). Downstream of Raudales de Guaharibos the gradient is 0.01% (183<ref name="gv">{{Cite web |title=Raudal de Guaharibos rapids, Estado Amazonas, Venezuela |url=https://ve.geoview.info/raudal_de_guaharibos,3640388 |access-date=2021-07-21 |website=ve.geoview.info}}</ref>/1,964), which is also the gradient from Ciudad Bolivar to the ocean (54/435).

=== Major rivers in the Orinoco Basin ===
* [[Apure River|Apure]]: from Venezuela through the east into the Orinoco
* [[Arauca River|Arauca]]: from Colombia to Venezuela east into the Orinoco
* [[Atabapo River|Atabapo]]: from the [[Guiana Shield|Guiana Highlands]] of Venezuela north into the Orinoco
* [[Caroní River|Caroní]]: from the Guiana Highlands of Venezuela north into the Orinoco
* [[Casiquiare canal]]: in SE Venezuela, a [[distributary]] from the Orinoco flowing west to the Negro River, a major affluent to the Amazon
* [[Caura River (Venezuela)|Caura]]: from eastern Venezuela (Guiana Highlands) north into the Orinoco
* [[Guaviare River|Guaviare]]: from Colombia east into the Orinoco
* [[Inírida River|Inírida]]: from Colombia southeast into the Guaviare.
* [[Meta River|Meta]]: from Colombia, border with Venezuela east into the Orinoco
* [[Ventuari River|Ventuari]]: from eastern Venezuela (the Guiana Highlands) southwest into the Orinoco
* [[Vichada River|Vichada]]: from Colombia east into the Orinoco
{{see also|Casiquiare canal-Orinoco River hydrographic divide}}